The recent acquisition of large numbers of night vision goggles by the U.S. Armed Forces has created an opportunity for use of covert, convenient and combat-safe area illuminators in the form of wavelength-selective flares, where the selected wavelength range is chosen to coincide with the range of wavelength for night vision that is provided by the night vision goggles. The flare unit should be small, preferably no larger than a cigarette package in size, should carry its own energy supply, should provide some means of controlling the direction of the illumination provided by the flare, and should provide some means for selecting the wavelength range that is emitted by the flare unit for illumination purposes.
Conventional flares have been known for more than half a century. Wiley, in U.S. Pat. No. 1,781,621, discloses a flare device that is initially attached to an aircraft; the flare can be launched by a spring unit from the aircraft at an appropriate time as the flare material is activated, to provide illumination for aircraft maneuvers or landing and takeoff.
A conventional flare supporting and firing device is disclosed in U.S. Pat. No. 1,937,219, issued to Driggs. This device is also designed to be attached to an aircraft and uses an activatable powder charge to expel the flare from the aircraft and illuminate the chosen area. Another patent by Driggs, U.S. Pat. No. 1,937,220, discloses an invention that is similar to the other Driggs invention but uses a metal closure cap to retain the flare when the flare is not to be activated.
Stirrat et al, in U.S. Pat. No. 4,158,323, discloses a flare dispensing system that mounts a plurality of flares on a module that is hung or tethered from an aircraft or helicopter. The flares are individually released and activated, and the flares fall toward the ground and provide illumination of a region of ground beneath the activated flare. The released flare may be carried in a parachute to reduce the vertical velocity and thereby increase the time interval during which illumination is provided by the activated flare.
None of these inventions discloses a flare device of small size that emits radiation only in a predetermined wavelength range, whose radiation can be focused or directed primarily in a narrow cone of directions to selectively illuminate a particular area, and that can be reused.
One object of this invention is to provide a self-contained flare unit that is small, carries its own energy supply, can be activated and deactivated at will, and can be reused.
Another object of this invention is to provide a flare unit where the radiation can be controllably focused for illumination of a particular area.
Another object of this invention is to provide a flare unit for which only a selected range of radiation wavelength is emitted for illumination purposes.
These objects, and advantages thereof, will become clear by reference to the detailed description and the accompanying drawings.